The U.S. government "kill[s] people based on metadata," but it doesn't do that with the trove of information collected on American communications, according to former head of the National Security Agency Gen. Michael Hayden.

Hayden made the remark after saying he agreed with the idea that metadata - the information collected by the NSA about phone calls and other communications that does not include content - can tell the government "everything" about anyone it's targeting for surveillance, often making the actual content of the communication unnecessary.

"[That] description… is absolutely correct. We kill people based on metadata. But that's not what we do with this metadata," said Hayden, apparently referring to domestic metadata collection. "It's really important to understand the program in its entirety. Not the potentiality of the program, but how the program is actually conducted.

"So NSA gets phone records, gets them from the telephone company, been getting them since October of 2001 from one authority or another, puts them in a lockbox… and under very strict limitations can access the lockbox," Hayden said and then described a hypothetical situation in which a number connected to a terrorist could be run against the metadata already collected to help investigators find additional leads in the name of national security.

"What it cannot do are all those things that… allows someone to create your social network, your social interactions, your patterns of behavior. One could make the argument that could be useful, [or] that could be illegal, but it's not done," he said. "In this debate, it's important to distinguish what might be done with what is being done."

Hayden, who served as NSA head from 1999 to 2005 followed by a stint running the CIA from 2006 to 2009, made the remarks early last month while discussing the NSA's mass domestic and foreign surveillance programs at Johns Hopkins University's Foreign Affairs Symposium.

David Cole, a professor at Georgetown University Law Center who was Hayden's foil in the discussion, this weekend wrote in the New York Review of Books that Hayden's remarks were evidence that arguments from government officials that there is little threat to privacy from metadata collection is "misleading." In the April discussion, Cole noted President Barack Obama's remarks to reporters last June, as media reports based on leaks by from former NSA contractor Edward Snowden were just beginning, in which he said, "Nobody is listening to your telephone calls."

"They are not looking at people's names, they're not looking at content," Obama said then. "But by sifting through this so-called metadata, they may identify potential leads with respect to folks who might engage in terrorism."

"We cannot discount the risk, in light of the lessons of our own history, that at some point in the future, high-level government officials will decide that this massive database of extraordinarily sensitive private information is there for the plucking," the President's Review Group on Intelligence and Communications Technologies said in a 300-page report.

As to the U.S. government "kill[ing] people based on metadata," two months before Hayden's comments, The Intercept reported on the NSA's purported role in America's drone program, which has been responsible for thousands of deaths on foreign soil in recent years. The report, based on the claims of a former drone operator and allegedly supported by documents provided by Snowden, said the government uses information about phone calls, but not necessarily their content, in tracking targets for lethal action.

The NSA declined to comment on the Intercept report at the time of its publication and today was not able to immediately provide comment for this report in response to Hayden's remarks.